UKAEA Journals

Showing 21 - 30 of 64 Journals Results
2014

A model system of equations has been derived to describe a toroidally rotating tokamak plasma, unstable to Resistive Wall Modes (RWMs) and metastable to Neoclassical Tearing Modes (NTMs), using a linear RWM model and a nonlinear NTM model. If no wall is present, the NTM growth shows the typical threshold/saturation island widths, whereas a linearly…

Published
2014

ITER’s Ion Cyclotron Range of Frequencies (ICRF) system [1] comprises two antenna launchers designed by CYCLE (a consortium of European associations listed in the author affiliations above) on behalf F4E for the ITER Organisation (IO), each inserted as a Port Plug (PP) into one of ITER’s Vacuum Vessel (VV) ports. Each launcher is an array of 4 …

Published
2013

Solutions to a model global 2D eigenmode equation describing micro-instabilities in tokamak plasmas are presented that demonstrate a sensitivity of the mode structure and stability to plasma profiles. In narrow regions of parameter space, with special plasma profiles, a maximally unstable mode is found that balloons on the outboard side of the toka…

Published
2012

Lower hybrid current drive (LHCD) with modest powers ( 10% of the total power input) has been used for the first time to completely stabilize performance limiting neoclassical tearing modes in many COMPASS-D tokamak discharges. The stabilizing effect in these experiments is consistent with a reduction in the free energy available in the current pro…

Published
2012

Plasma equilibria reconstructed from the Mega-Amp Spherical Tokamak have sufficient resolution to capture plasma evolution during the short period between edge-localized modes (ELMs). Immediately after the ELM, steep gradients in pressure, P , and density, n e , form pedestals close to the separatrix, and they then expand into the core. Local gyrok…

Published
2011

Pedestal profiles that span the ELM cycle have been obtained and used to test the idea that the pedestal pressure gradient in MAST is limited by the onset of Kinetic Ballooning Modes (KBMs). During the inter-ELM period of a regularly type I ELM-ing discharge on MAST, the pressure pedestal height and width increase together while the pressure gradie…

Published
2010

A Thomson scattering diagnostic designed to measure both edge and core physics has been implemented on MAST. The system uses eight Nd:YAG lasers, each with a repetition rate of 30 Hz. The relative and absolute timing of the lasers may be set arbitrarily to produce fast bursts of measurements to suit the time evolution of the physics being studied. …

Published
2009

The formation of neoclassical tearing modes (NTMs) severely limits the performance of a tokamak plasma by increasing the radial particle and heat fluxes from the core and can even lead to a plasma disruption. Indeed, NTMs are a serious consideration for the next step device, ITER. The appearance of a finite NTM magnetic island requires an initial …

Published
2009

The H-mode pedestal characteristics on MAST are measured in a variety of Connected Double Null (CDN) and Single Null Divertor (SND) discharges. In CDN discharges the edge density pedestal width in spatial co-ordinates is similar on both the high and low field sides suggesting that the width may be determined by neutral penetration. However, in SND …

Published
2009

Within the framework of the International Energy Agency, an international collaborative study on fusion radioactive waste has been initiated to examine the back end of the materials cycle as an important stage in maximizing the environmental benefits of fusion as an energy provider. The study addresses the management procedures for radioactive mate…

Published